The present invention relates in general to semiconductor technology and in particular to Schottky diode structures and methods of manufacturing the same.
Schottky diodes are semiconductor devices which have a metal-semiconductor transition as their basic structure and whose basic electronic properties are defined by this transition. A Schottky diode is formed from a metal-semiconductor combination which is chosen such that a depletion zone arises at the boundary surface.
FIG. 1 shows a cross-section view of a portion of a conventional Schottky diode. Schottky diode 100 is formed by a metal layer 102 contacting a semiconductor region 104. When Schottky diode 100 is turned on, current travels in a vertical direction from the metal layer 102 to the semiconductor region 104. In such devices, the electric field decreases linearly from its maximum at the metal-semiconductor boundary surface, or Schottky barrier, through the semiconductor region 104 at a rate dictated by the doping concentration of the semiconductor region 104. In addition, the semiconductor region 104 doping and thickness is tailored for a given blocking voltage, or breakdown voltage.
However, in the mid to high voltage range (e.g., 60 to 2000 volts), conventional Schottky diodes suffer from power loss primarily due to the high resistivity of the semiconductor region (e.g., semiconductor region 104 in FIG. 1). The semiconductor region has high resistivity because in order for the device to sustain the high voltages during the blocking state, the semiconductor region is lightly doped. The high resistivity of the semiconductor region results in a higher on-resistance, which in turn results in high power loss. Since a high blocking voltage is a critical feature for mid to high voltage power devices, increasing the semiconductor region doping is not an option.
Thus, a technique which enables achieving a high device blocking capability, low on-resistance, and high current handling capability is desirable.